How to Make It
Preheat oven to 375°. Cut spaghetti squash in half lengthwise; discard seeds. Bake squash, cut sides down, on a lightly greased (with cooking spray) baking sheet 40 to 45 minutes or until tender. Cool 10 minutes. Scrape inside of squash to remove spaghetti-like strands.
Whisk together buttermilk, cream, eggs, Parmesan cheese, and salt in a large bowl. Process half of squash strands in a food processor until smooth; stir into cream mixture. Process squash-cream mixture in batches until smooth.
Return mixture to bowl, and stir in cornbread and remaining squash. Let stand at room temperature 1 hour.
During last 20 minutes of stand time, place a 12-inch cast-iron skillet in oven, and preheat oven to 375°. Add butter to skillet, and tilt to coat sides and bottom. Transfer squash mixture to skillet.
Bake at 375° for 35 to 40 minutes or until a wooden pick inserted in center of spoonbread comes out clean. Cool 5 minutes before serving.